This invention relates to a compressor for compressing refrigerant circulating through an air-conditioning unit for automotive vehicles.
Conventionally, a compressor of this kind has been disclosed, e.g. by U.S. Pat. No. 4,815,945. As shown in FIG. 1, this compressor comprises a cylinder formed by a cam ring 1 having an inner peripheral surface 1a with a generally elliptical cross section, and a front side block 3 and a rear side block 4 closing open opposite ends of the cam ring 1, a cylindrical rotor 2 rotatably received within the cylinder, a front head 5 and a rear head 6 secured to outer ends of the respective front and rear side blocks 3 and 4, and a driving shaft 7 on which is secured the rotor 2.
A pair of compression spaces 12 are defined by the front and rear side blocks 3, 4, and the rotor 2, and a discharge pressure chamber 10 is defined by the front side block 3 and the front head 5. Refrigerant outlet ports 16 are formed through lateral side walls of the cam ring, and a communication chamber 20 is defined by each lateral side wall of the cam ring 1 and a corresponding discharge valve cover 17. A communication passage 30 is formed through the front side block 3 and communicates the communication chamber 20 with the discharge pressure chamber 10.
Refrigerant gas discharged from the compression space 12 flows into the discharge pressure chamber 10 via the refrigerant outlet ports 16, the communication chamber 20, and the communication passage 30.
The refrigerant gas discharged into the communication chamber 20 from the compression chamber 12 is under pulsation, and the pulsating refrigerant gas directly flows into the discharge pressure chamber 10 via the communication passage 30, causing vibrations in the longitudinal directions of the compressor. The frequency of the vibrations is approximately equal to ten times the number of revolutions per second of the rotor 2. For example, if the number of revolutions per second of the rotor is 30, the frequency of the vibrations is 300 Hz. Thus, the conventional vane compressor, when installed in an automotive vehicle, generates vibrations having a frequency of 300 to 800 Hz, so that other components of the automotive vehicle vibrate by resonance to cause offensive noise.
Therefore, the occurrence of noise due to vibrations caused by the flow of the refrigerant gas into the discharge pressure chamber can be prevented by attenuation of pulsation of the refrigerant gas.